Dehydrogenation of paraffins, particularly lower paraffins such as propane or butane, to obtain corresponding olefins is an endothermic reaction. The process is traditionally carried at high temperatures, such as between 550° C. and 650° C., and in the presence of a metal-based catalyst. Due to the high temperature, the catalyst is quickly and easily coked, and the period of time during which the catalyst is stable is limited, in some instances to minutes or even seconds.
While the stability of the catalyst can be somewhat improved by using it in a form of a fluidized bed, traditional catalytic dehydrogenation of paraffins has other drawbacks and deficiencies besides problems with stability. For example, in traditional catalytic dehydrogenation many catalysts cannot withstand many cycles of regeneration and heat integration without substantial loss of activity and selectivity. The ability of catalysts to promote selective reactions (i.e., reactions leading to the formation of the desired final product) is also limited in traditional processes, and the share of thermal, non-selective reactions (i.e., reactions leading to the formation of the products other than the desired product) is often larger then desired.
One class of non-noble metal dehydrogenation catalysts that was previously described includes molybdenum oxides on a support, e.g., MoOx on gamma-alumina or ZrO2 that may have activity similar to that of platinum based catalysts, such as Oleflex™ catalysts. However, such MoOx/Al2O3 or MoOx/ZrO2 catalysts are often characterized by poor hydrothermal stability usually leading to a quick loss of activity. Catalysts that include calcium or yttrium-stabilized ZrO2 also may lose significant surface areas to coke contamination, also leading to the eventual loss of activity. In addition, in case of calcium-stabilized substrates, an inactive material CaMoO4 may be formed, which is undesirable.
The above-mentioned and other drawbacks and deficiencies of traditional catalytic dehydrogenation of paraffins have not been resolved. To improve the overall efficiency of dehydrogenation, it is desirable to have catalysts possessing better activity, stability and selectivity. Ideally, thermal, non-selective reactions should be eliminated or at least substantially decreased. To achieve these ends, better catalysts are needed, particularly those that are hydrothermally stable, so that the catalysts can retain their stability and selectivity when the regenerated catalyst is subjected to high temperatures. It is also very desirable to have a catalyst that may be regenerated with a carbon burn.